The problem is, by the time you realize you have been used by a psychopath, they have moved on; usually up the company ladder to a position of trust and power amoung their new "victims" where at best, anything you have to say won't be believed; at worst, your own career is at risk.

The impact on team performance is significant. The first to leave are your top talent because they have the most options and won't put up with this behavior. Others may stay but take on a heads down, everyone for themselves demeanor. The more senior the role of the psychopath, the more acceptance there seems to be for poor behavior. Whether you like or dislike unions, this is a situation where they can be very helpful for employees in this type of situation. For many non-unionized employees they have little to no recourse other than accept it or leave. HR is usually of little help, and frequently protects the senior individual.